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Evidence Based Practice

Use this guide to learn about the first four steps of Evidence Based Practice, get help writing your PICO question, and get started on your research.

Align: Levels of Evidence

(Image: EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.)

​Study designs are placed into a hierarchy based on their reliability (probability of bias) known as the Levels of Evidence

The Levels of Evidence are often represented by a pyramid, with the highest levels of evidence (least common) near the top, and the lowest levels of evidence (most common) near the bottom.  The pyramid above is based on the Oxford Centre for Evidence Based Medicine's rating system for therapeutic studies, but a variety of rating systems exist.


Types of Study Design:


Question Type & Study Design

Some study designs are better suited to answer certain types of questions. Identifying the clinical domain your question falls under can help determine what study designs to look for in order to find the best, most suitable evidence.  Systematic Reviews and Meta-Analyses are always preferred.

Check off the clinical domain and preferred study design type on the Well-Built, Patient-Oriented Clinical Question worksheet. The link to that worksheet can be found above.

Clinical Domain

Preferred Study Design (after systematic reviews and meta-analyses)

Cost-Effectiveness Economic Analysis
Diagnosis Cross-Sectional Studies or Gold Standard
Etiology or Prognosis Cohort > Case-Control > Case Series
Prevention Randomized Controlled Trial > Controlled Trial > Cohort > Case-Control
Quality of Life Qualitative Studies
Therapy Randomized Controlled Trial > Controlled Trial or Quasi-Experimental Studies
For example:
Clinical question: In adult patients with total hip replacements, how effective is pain medication compared to aerobic stretching in controlling post operative pain during the perioperative and recovery time?
Clinical domain: Therapy
Preferred study designs: Systematic Reviews, Meta-Analyses, Randomized Controlled Trials, and Controlled Trials


Click "Next" to learn about the Acquire Step.